Railway signal systems



Oct. 23, 1956 H A. THOMPSON RAILWAY SIGNAL SYSTEMS 3 Sheets-Sheet 1 Filed Feb. 9, 1955 w ER . INVENTOR. Howard A. Thompson BY w.1 .m

131s ATTORNEY Oct. 23, 1956 H. A. THOMPSON RAILWAY SIGNAL SYSTEMS 5 Shets-Sheet 2 Filed Feb. 9, 1953 .n 0 mm, W W W W 1 0. K, d w W H 0V. HB j a v5 1$ lm N EQ wfi kw m I p i Oct. 23, 1956 H. A THOMPSON RAILWAY SIGNAL SYSTEMS 3 Sheets-Sheet 3 Filed Feb. 9, .1953

Y mm m A M A wwm W 0 fi wmwwwumwl United States atent O RAILWAY SIGNAL SYSTEMS Howard A. Thompson, Edgewood, Pa., assignor to Westinghouse Air Brake Company, Wilmerding, Pin, a corporation of Pennsylvania Appiicatlon February 9, 195! Serial No. 335,633

8 Claims. (Cl. 246-5l0) My invention relates to railway signal systems and particularly to wayside signals which provide a substantially continuous visual indication to the train operator as to traffic conditions in advance.

Continuous cab signal systems provide a high order of control because the cab signal is constantly visible to the train operator and the signal indication is immediately responsive to changes in trafiic conditions in advance. This continuous control for cab signals is accomplished through the mounting of train-carried elements and trackway elements in such a manner that the train elements are constantly in operating relationship with the track elements. Thus these cab signal systems require each locomotive or motor car to be equipped with the train-carried portion of the apparatus. in order to have the advantages of the protection afforded by the signal system. When it is necessary to move locomotives of other railroads or unequipped. locomotives over this ter ritory extra precaution must be takenbecause these trains are without the, cab signal protection. Also, such cab, signal systems are relatively expensive and ordinarily they are economically justified only on roads of relatively dense trafiic,

There is a demand for signal systems that will provide substantially the high order of protection; aiforded' bycontinuous cab signals at, a relatively low initial cost: and maintenance. Also, that each trainto have the protection of the signal system will not have to be equipped with a train-carried portion of the apparatus.

Furthermore, there is. a demand forsignal systems of the type here contemplated that. use track circuits having a shunting sensitivity that improves the response of the track circuit to lightweight rolling stock, such as motor cars. Again, there is a demand for signal systems to which there can be applied means for controlof highway crossing signals in an inexpensive and simple manner. Again, there is a demand for signal systems arranged insuch a manner as to enforce a reduced speed at curves and at other permanent track hazards.

Accordingly, an object of my invention isthe provision of improved railway signal systems incorporating wayside signals that are substantially continuously visible to the operator of a train moving over the territory'and' which signals immediately change their indications when trackway conditions in advanced a train change;

Again, an object of my invention is the provision of Wayside railway signal systemswhich provide a control which is substantially the equivalent of that ofcontinuous cab signal systems.

A feature of'my invention is the provision oflwayside' a wayside railway signaling systemincorporating novel means for enforcing a reduced speed'at curves and other permanent-hazards. 1

2,768,285 Patented Oct. 23, 1956 A further feature of my invention is the provision of railway signal systems of the type here involved which are relatively low in cost and maintenance.

Another feature of my invention is the provision of railway signal systems incorporating novel track circuits that can be arranged to provide highway crossing signal control without additional cut sections;

Other objects, features and advantages of my invention will appear as the specification progresses.

In the forms of the invention here disclosed I attain the foregoing objects, features and advantages of my invention by arranging a stretch of railway track into consecutive insulated blocks each of which may be provided with automatic signals according to the usual practice. Each of these blocks is formed with a series of relatively short track sections, each of which sections is equipped with a track circuit having a track relay located at the exit end of the section and a source of current connected to the rails at the entrance end of the section. A short range wayside signal is provided for each track section, these signals being substantially continuously visible one at a time to a train as it moves through the associated sections due to the shortness of the sections.

Each automatic block is provided with a polarized line circuit which is supplied with current of positive or negative polarity according to trafiic conditions in advance. At the entrance end of each of the short track sections there is provided a polar relay which is interposed in the, line circuit by the approach of a train and this relay is used to govern the respective short range signal, the indication displayed by this signal reflecting the condition of trafiic in advance. Thus these short range signals are controlled one at a time and there is a signal constantly visible tothe trainoperator due to the short spacing of the signals. Also, the indication displayed by these signals is immediately changed when traffic conditions in advance cause a change in the indication of the block signal in advance. The signal lamps of these intermediate short range signals are powered over the line circuit and a local power supply at each track section is notrequired. In this way a wayside signal that reflects trafiic conditions in advance is made visible substantially constantly to the train operator and the operator is informed immediately when trafiic conditions:

in advance change.

The track circuits for the'track sections being relatively short, they are characterized by high shunting sensitivity and ahigh order of broken rail protection. Also, these.

short track circuits can be readily arranged to provide, control for highway crossing signals without additional [shall describe certain forms of wayside railway signal.

systems embodying my invention and shall then point out the novel features thereof in claims.

In the accompanying drawings, Fig. l is a diagram matic view showing one form of apparatus for a rail- Way signal system embodying my invention.

Figs. 2a and 211 when placed end to end with Fig. 2a.

at the left are diagrammatic views showing another form of; apparatus embodying the invention and wherewitli speed :controlfor curves is provided.

Fig. 3 is a schematic view showing one form of locomotive circuits that may be used to cooperate with the wayside apparatus shown in Figs. 2a and 2b.

In eachof the several views like reference characters are used to designate similar parts.

Referring to Fig. 1, the reference characters 3 and 4 designate the rails of a stretch of railway track over which trafiic moves in the direction indicated by the arrow, that is, from left to right or from west to east. These rails of this stretch of track are formed by the usual insulated rail joints with consecutive blocks of which the location D is the entrance end and the location E is the exit end of a block D-E. Obviously, the location D is also the exit end of the block next to the left, or west, of block D-E and the location B is the entrance end of the block to the right or east of the block DE. Only the one block D-E and adjacent ends of the two adjacent blocks are shown since the arrangement of the blocks are substantially alike and the showing in Fig. l is sufficient for an understanding of the invention.

A wayside signal SD is provided at location D for governing trafiic entering the block D-E. Similarly, a wayside signal SE is provided at location B for governing traffic moving into the block to the east. These wayside block signals SD and SE may be any one of several known types and are shown as color light signals adapted to display a green light G as a clear signal indication, a yellow light Y as an approach signal indication and a red light R as a stop signal indication. Each block signal is operated by a local source of current controlled by trafl'ic conditions in advance. To this end each block signal location is provided with a source of direct current, the positive and negative terminals of which are designated B and N, respectively. Looking at the signal SD, for example, the operating circuits are governed by two line relays DHR and DDR, together with an approach controlled contact 13, the arrangement being such that when relays DHR and DDR are picked up closing front contacts 14 and 15, respectively, and the approach contact 13 is closed, a circuit is completed from terminal B through contact 13, front contact 14 of relay DHR, front contact 15 of relay DDR, and lamp G of the signal SD toterminal N of the power source, and the lamp G is illuminated causing signal SD to display a clear signal indication. When relay DHR is picked up and relay DDR is released, then a signal operating circuit is completed. fromterminal vB through approach contact 13, front contact 14 of relay DHR, back contact 15 of relay DDR and lamp-Y to terminal N, and the lamp Y is illuminated causing signal SD to display an approach signal indication. Again, when relay DHR is released a circuit is completed from terminal B through approach contact 13, back contact 14 of relay DHR, and lamp R to terminal N, and lamp R is illuminated causing the signal SD to display a stop signal indication. Similarly, the operating circuits for signal SE are controlled by two line relays EHR and EDR and an approach contact 32, as will be apparent by an inspection of Fig. 1. The manner by which the line relays DHR and DDR at location D and the line relays EHR and EDR at location E are controlled will be described hereinafter.

According to my invention, the track rails of the block DE are formed by the usual insulated rail joints into a series of relatively short track sections, it being understood that each of the other blocks is formed in a similar manner into a series of short insulated track sections. As shown in Fig. 1, the block D-E is formed with five track sections, designated 1T to T, inclusive, but it is to be understood that the invention is not limited to any particular number of track sections and more than five or less than five track sections for each block can be used. These track sections may be of substantially equal lengths but track sections unequal in length can be provided. In fact, when the track includes curves, then the track sections located at a curve will be somewhat shorter, because preferably the track sections are of a length such that under ordinary weather conditions visibility is obtained from the exit end of the section to the entrance end of the section. As an aid in the understanding of the invention, it may be assumed that the block D-E is of the order of 10,000 feet in length, and each of the five track sections is of the order of 2,000 feet in length, but it is clear that some of the track sections may be longer and some may be shorter.

Each track section IT to ST is provided with a track circuit that includes a source of current connected across the rails adjacent the entrance end of the section and a track relay connected across the rails adjacent the exit end of the section. Looking at the track section 1T, for example, the track circuit includes a battery 10 connected across the rails at the left-hand or entrance end of the section, and a track relay 1TR connected across the rails at the right-hand or exit end of the section. As here shown, each of these track circuits is of the polarized type and the track relay is of the polar biased neutral type, such relays being known to the art. That is, the contacts 11 and 12 of the track relay 1TR are polar biased as well as gravity biased to a released position closing back contacts, and are picked up by closing front contacts only when current of a given polarity flows in the relay winding. The arrangement is such that the contacts 11 and 12 of the relay winding 1TR are picked up closing front contacts only when current flows in the relay winding from the left-hand terminal to the right-hand terminal, that is, in the direction indicated by the arrow placed on the relay winding. When current flows in the relay Winding in the direction reverse to that indicated by the arrow,

' deenergized.

that is from the right-hand terminal to the left-hand terminal as viewed in the drawing, the contacts 11 and 12 are released closing back contacts, and these contacts 11 and 12 are also gravity released when the relay is It follows that with the track battery 10 connected across the rails of the section IT and the polarity indicated by the plus and minus signs, the rail 3 is positive with respect to rail 4, and current flows in the winding of relay 1TR from left to right and the relay is picked up closing its front contacts 11 and 12 when the section is unoccupied, but that when the rails are shunted by a train occupying the section, the track relay ITR is deenergized and released closing back contacts 11 and 12.

Similarly, each of the other sections 2T, 3T, 4T and ST is provided with a track circuit similar to that provided for the section 1T. It is to be observed that the plurality of the rails is reversed for adjacent sections to provide broken down insulated rail joint protection in the well-known manner.

It is clear'that with the track circuits here provided a relatively high order of shunting sensitivity is achieved because of the relatively short length of the track sections and due to the polar biased neutral type of track relay. Also, broken down insulated rail joint protection and a high order of broken rail protection are obtained. Furthermore, when highway crossing signal control must be provided, the approach control of the highway crossing signal can be readily achieved by properly arranging the short track sections of the signal system and the usual cut section location can be avoided. In addition, a high reliability of operation of the track circuits is effected because the ballast leakage current of each of the short track sections will be low.

Each track section of this series of sections, except the first section IT, is provided with an auxiliary wayside signal identified by the reference character S, plus a numeral corresponding to the numeral of the track section, the signals 28 to 58 being provided for the sections 2T to 5T, respectively. 7

Each of these auxiliary signals is located adjacent the entrance end of the respective section and preferably the signals are of a low pedestal short range type, such as the welbknown dwarfsignal. As sheen, the auxiliar signals are of the color light type, each signal being provided with a green light G for displaying a 'c1ea'r signal indica tion, and a yellowlight Y for displaying a restrictive signal indication. These signals may be of a construction that permits them to be mounted between the track rails and set low enough so "as not to extendabove the top of the rails, but as illustrated the signals are shown located just outside of the rails to the right-hand side. The essential feature of these auxiliary signals is that each is visable for substantially the full length of the section. Thus, at curves the length of the associated track section would be short enough to assure visibility of the auxiliary signal located at the exit end of the section so that there is always a wayside signal visible to the train operator except under the most severe stormy or foggy conditions, and then a signal would be visible except for a portion at the entrance end of each track section. That is, as the head end of the train passes one of the auxiliary signals, the nextauxiliaryvsignal becomes visible to the operator so that there is substantially a continuous display of a wayside signal to the operator as the train passes through the different track blocks, it being observed that for the last track section T, the signal displayed to the operator is the blcck signal.

Each block is provided with a two-wire line circuit for control of the associated block signal and control of the associated auxiliary signals. In Fig. 1, the line circuit is a polarized circuit including line wires lLW and 2LW extending the full length of the block and to which direct current of positive or negative polarity is supplied by a source at the location E according to trafiic conditions in advance of the block. In the form of the invention shown in Fig. 1, the line circuit current is also coded by being recurrently interrupted at a selected code rate. Under a first traflic: condition in advance of block D-E with the relay EHR. energized in a manner to appear hereinafter, line wire lIW is connected to terminal B of the power source at locationE through front contact 16 of relay EHR and Contact 17 of a code transmitter 75CT, and line wire: 2LW is connected to terminal N of the currentsource' through front contact 18 of relay EHR. Under a second. trafiic condition in advance of block D-E With the line relay EHR released closing back contacts 16 and 18, theconnection of the line wires lLW and ZLW to the current source is pole changed. Thus, under the first trafiic condition current of what I shall call positive polarity is supplied to the line circuit and under the second traffic con-- dition the line circuit is supplied with current of negative polarity, the line circuit current being recurrently interrupted by the code transmitter 75CT under each name condition.

The code transmitter 75CT may be of any one of the several known types and, for example, it maybe of the:

relay type whereby its contact 17 is recurrently opened. and closed at a selected code rate as long as current is supplied to its operating winding. I shall assume that the: code transmitter 75CT is operated at a code rate of 75 times per minute and thus the line circuit current is: recurrently interrupted at the code rate of 75 times per minute. It will be understood that the invention is not: limited to a code rate of 75 interruptions per minute and. other code rates may be used. Furthermore, the invention is not limitedto a coded line circuit current and as Will. appear when the form of the apparatus disclosed in Figs. 2a and 2bis described, a-noncoded line circuit current can. be used.

The line relay DHR is connected across the line circuit lLW-ZLW through a full wave rectifier 19 and. is energized when current. of either polarity is supplied to the line circuit. The. relay DHR is provided with slow release characteristics due to the snuhhing action of'the rectifier 19 and hence. the relay does not release during; thepole changing action of the line circuit and does not; release: between the code pulses of the current;

. ans

A half wave rectifier 20 is interposed in series with the line wire ZLW at location D and the winding of the relay DDR is connected across rectifier 20. Relay DDR 'is a polar biased neutral relay similar to the track relay ITR and is arranged so that its contact 15 is picked up closing its front contactonly when current flows in the winding of the relay from left to right as indicated by the arrow placed on the relay winding; It follows that when current of positive polarity is supplied to the line circuit and the line wire lLW is positive with respect to the line wire 21MB", current is substantially blocked bythe rectifier 2t) and it flows in the winding of the relay DDR froni left to right so that the relay is picked up closing its front Contact 15. When the line circuit current is of negative polarity and the line wire 2LW is positive with respect to the line Wire lLW, the current is passed by the rectifier 23 in its forward direction and the relay DDR is deene'rgized and released, closing its back contact 15, Consequently, under the first traffic conditions that cause current of positive polarity to be supplied to the line circuit ElLW-ZLW at location E, both relays DHR and DDR at location D are picked up, but under the second traffic condition that causes current of negative polarity to be supplied to the line circuit at location E, the relay DHR is picked up and the relay DDR is released. Furthermore, when any of the track relays for the sections of the block 13-15 are released this to a train occupying the respective track section, then the line circuit lLW-ZLW is open and without current in a manner to be explained hereinafter and both relays DHR and DDR are released.

It is to be pointed out that the line relays EHR and EDR at locaticn E are connected to the line wires SLW :ancl 4LW of the line circuit for the block next to the right in the same manner as the line relays DH and DDR :are connected to the line circuit 1LW,2LW,and it fol- .lows that when current of positive polarity is supplied to the line circuit 3LW4LW in response to a first traflic :condition, both relays EHR and EDR and picked up, but that under a second traffic condition and current of negaitive polarity is supplied to the line circuit 3LW4LW, the relay EHR is picked up and the relay EDR is released. .Also, when the line circuit is deenergized then both relays EHR and EDR are released.

Again, it is to be observed that the line relay DH-R and :a code transmitter at location D control the supply of current to the line wires 5LW-6LW of the line circuit for the block next to the left in the same manner that the relay EHR and the code transmitter CT at locaft-ion E govern the supply of current tothe line circuit 12LW2LW.

:Each auxiliary signal location in block D-'E isproviiled with a line relay designated DR plus a prefix corresponding to the reference character of the associated auxiliary signal. These line relays are energized by the li'ne circuit 1LW-2LW and each controls the lamp circuits of the associated signal. Looking at the location of signal 28, for example, a line relay ZSDR is connected across a half wave rectifier 21 interposed in series in the line Wire ZLW. This line relay ZSDR is of the polar biased neutral type similar to the line relay DDR. and is arranged for its contact 22 to be picked up only when current flows in the winding of the relay from left to right as indicated by the arrow placed on the relay winding. Similarly, the locations of the auxiliary signals 38, 4S and 58 are provided with line relays 3SDR, 4SDR and SSDR, respectively, and each of these relays is connected across a half wave rectifier interposed in the line wire ZLW. The manner by which these line relays are energized and in turn control the local auxiliary Wayside signal can be explained best by describing the operation of the apparatus.

In describing the operation of the apparatus of Fig. 1, the apparatus is shown in its normal position, that is, in the position it assumes when this stretch of track is un occupied. In this normal position, the track relays and theline relays are energized and picked up, the line circuit being supplied with current of positive polarity. The blocksignals and the auxiliary signals are dark due to the approach control feature. Assuming a train moving in the normal direction of traffic, that is, from left to right, approaches the signal SD, a track relay ATR for the section next in the rear is shunted, closing back contact 13, and approach controlling the signal SD, the circuit for the green light G of signal SD being completed and the signal SD displaying a clear signal indication. When the train moves past the signal SD and enters the track section 1T, the track relay 1TR is shunted and the relay released closing back contacts 11 and 12. The opening of the front contacts 11 and 12 of the track relay 1TR removes the line wires lLW and ZLW extending to the rear of signal 28 from the line circuit so that the line relays DHR and DDR are deenergized and released with the result that the green light G for the signal SD is extinguished and the red light R is illuminated causing the signal SD to display a stop signal indication. The closing of back contact 12 of track relay llTR cornpletes a shunt path across the line wires 1LW and ZLW to the rear as an additional precaution that the line relays DHR and DDR are deenergized. The closing of back contact 11 of the track relay 1TR completes a circuit from the line wire 1LW to the east of signal 23 through a resistor 23 and the winding of relay ZSDR from left to right to the line wire 2LW since at this time the line circuit current is of positive polarity and is blocked by the rectifier 21. The closing of back contact 11 of the track relay lTR also completes a circuit path by which current flows from the line wire 1LW through back contact 11, front contact 22 of relay 2SDR, green lamp G of the auxiliary signal 28, and to the negative wire 2LW, and lamp G of signal 2S is illuminated causing the signal 25 to display a flashing green signal indication. This signal 28 will ordinarily be continuously visible to the train operator as the train moves through the section 1T due to the relatively short length of the section.

When the train passes the signal 28 and enters the track section 2T, the track relay 2TR is shunted and released to open its front contacts 24 and 25 and close the corresponding back contacts. The opening of front contacts 24 and 25 removes current from the line wires 1LW and 2LW to the west of signal 38 so that the line relay 2SDR and the lamp circuit for the signal 25 are without current. Also the line relays DHR and DDR remain deenergized. The closing of back contact 25 of relay 2TR places a shunt across the line wire to the rear of signal 38. The closing of back contact 24 completes a circuit path by which current flows from the line wire lLW through resistor 26, winding of relay SSDR from left to right and to line wire 2LW and the relay 3SDR is energized and picked up so that the lamp G of the signal 38 is now illuminated by current flowing from line wire 1LW through back contact 24 of relay 2TR, front contact 27 of relay 3SDR and green lamp G of signal 38 to line wire 2LW. This causes the signal 3S to display a flashing green light to the train approaching through the section 2T and the signal will be substantially constantly visible to the train operator because of the relatively short length of the track section.

Similarly, when the train enters section 3T, the track relay 3TR is shunted opening its front contacts 28 and 29 and closing the corresponding back contacts so that the line relay 4SDR is picked up and the lamp G of the signal 48 is flashed due to the current supplied from the line circuit. Again, when the train enters section 1T, the track relay 4TR is shunted opening its front contacts 39 and 31 and closing the corresponding back contacts so that the line relay SSDR is energized and the lamp G of the signal 58 is illuminated to display a flashing green light, and which signal indication is substantially constantly visible to the train operator due to the shortness of the track section 4T; When the train enters the last track section 5T, the track relay STR- is shunted closing back contact 32 and approach controlling the circuit for the lamp G of the block signal ES and thatsignal displays a steady clear signal indication, since at this time both line relays EHR and EDR are energized and picked up. Since the track section ST is relatively short, the signal SE will be visible substantially the full time that the train is moving through the section 5T. It follows from the foregoing description of the operation of the apparatus, that a wayside signalis displayed constantly to the operator asthe train moves through the block DE.

When this train enters the first track section for the block to the right of location E, the corresponding track relay, not shown, will be shunted and the line relays EHR and EDR will be without current in the same manner that the relays DHR and DDR are without current when the train occupies the section 1T. With the relay EHR released closing back contacts 16 and 18, current of negative polarity is applied to the line circuit ILW-ZLW. This causes the line relay DHR to be'picked up, but each of the line relays DDR, 2SDR, 3SDR, 4SDR, and SSDR will be deenergized since the line circuit current will pass through the corresponding rectifiers 20, 21, 33, 34 and 35 in the low resistance direction and also what current may flow in thewinding of these line relays will flow in the direction tending to release the relays.

Assuming that at this time a second train approaches signal SD from the left to shunt the track relay ATR and close back contact 13, the circuit for the lamp Y of the signal SD is completed and the signal SD displays an approach signal indication. When this second train enters section IT to shunt track relay 1TR, the line relay 2SDR remains deenergized and current flows from line wire ZLW through lamp Y of signal 28, back contact 22 of relay 2SDR and back contact 11 of relay 1TR to line wire lLW and consequently the signal 25 displays a flashing yellow light which is constantly visible to the train operator while the train advances through the section 1T. At this time current flows from the line wire ZLW through resistor 23, and back contact 11 of relay lTR to the line Wire 1LW, but the current provides no useful function and the leakage current is minimized by the resistor 23. That is, resistor 23 is made high enough to not shunt the signal lamp Y of sginal 2S. It is apparent that when the second or following train enters the section 2T and the first train is still in the block to the east, the shunting of the track relay 2TR will complete a circuit path by which the Y lamp of the signal 38 is illuminated and the signal 38 displays a flashing yellow signal indication, this signal being continuously visible to the train operator during the time the train is traveling the section 2T. Similarly, the Y lamp of the signals 45 and 58 will be illuminated and displayed when the following train occupies the sections 3T and 4T, respectively, if the leading train still remains in the block to the east. When the following occupies the last track section ST and the track relay 5TR is shunted closing back contact 32, the circuit path for the red lamp R of the signal SE is completed and this signal displays a stop signal indication due to the block to the east being occupied by the leading train.

Assuming that when the following train occupies the track section 3T and the signal 48 displays a flashing yellow light, the first or leading train moves east out of the block next to the right, then the line relay EHR is picked up and current of positive polarity is supplied to the line circuit 1LW2LW. With current of positive polarity applied to the line wires lLW and 2LW, current flows from the line wire 1LW through back contact 28 of the relay 3TR, resistor 36 and winding of relay 4SDR from left to right, to line wire 2LW, and the relay 4SDR is picked up closing its front contact 37 so that the signal circuit for signal 48 is switched from the yellow lamp Y to the green lamp G and signal 45 immediately displays a flashing green light. It follows from the foregoing that 9 the apparatus provided in Fig. 1 provides wayside signals that are substantially continuously visible one at a time to the train operator and which change their indication immediately upon a change of tratfic conditions in ad- Vance.

In the form of the invention shown in Figs. 2a and 2b, the track rails 3 and 4 of a stretch of railway over which traffic normally moves in the direction indicated by the arrow are arranged in consecutive blocks the same as in Fig. 1. Also, the block D-E of Figs. 2a and 2b is formed with relatively short track sections, there being 8 track sections IT to 8T, inclusive, shown in the drawings, but the specific number of track sections can be selected as best suited for the particular stretch of track. These track sections IT to 81 are provided with track circuits, the track circuits being of the same arrangement as the track circuits provided in the first form of the invention. Furthermore, a short range color light signal is provided for each of the track sections, except that there is a block signal provided for each block. in this second form of the invention, however, block signals may be omitted and a short range signal may be provided at the entrance end of each of the blocks if desired. A polarized line circuit is provided for the block D-E of Figs. 2a and 212 for control of the wayside signals,the same as in the first form of the invention, except the line circuit for the second form uses line relays of a different form and the circuits of each of the wayside signals is somewhat different. It is believed that this line circuit can best be understood by a description of the operation of the apparatus of Figs. 2a and 2b. Normally, that is, when the stretch is unoccupied, each of the track circuits is energized, the line circuit 1LW2LW is supplied with current of positive polarity and each of the wayside signals is dark due to the approach control arrangement. Under this normal condition the line relay EHRl at location E is energized due to current supplied from the line circuit 3LW-4LW to the east. With relay EHRl picked up closing front contacts 33 and 3%, the line wire llLW is connected to terminal B of the current source over front contact 40 of track relay dTR and front contact 33 of the relay EHRll, and line wire ZLW is connected to terminal N of the source over front contact 41 of track relay 8TR and front contact 39 of relay EHRl. This line circuit current is supplied to the relay DHRl at location D and that relay is picked up closing its front contacts 42 and. 43 so that current of positive polarity is in turn supplied to the line wires dLW and 6LW of the line circuit for the block to the rear. These line relays EHRI and DHRl are of the retained neutral type, such relays being known to the art. That is, these relays when energized and picked up by current of one polarity will retain their front neutral contacts closed when the polarity of the energizing current is reversed and the magnetic flux of the relay dies down, passes through zero and builds up in the reverse direction. 7

Assuming an eastbound train approaches the block D-E, the track relay ATR for the track section to the rear of the block is shunted opening front contacts 50 and 51 and closing back contacts 4 and 45. The opening of front contacts 59 and 51 removes current from the line circuit to the rear, the closing of back contact 45 prepares the operating circuit for the signal 18 and the closing of back contact 44 completes a circuit path for ener gizing the line relay DDR, current flowing from line wire ILW through back contact 44, and winding of relay DDR from left to right to the line wire ZLW so that relay DDR is picked up closing its front contact 46 and completing the circuit for the lamp G of signal 18 with the, result that the signal 18 displays a clear signal in 10 to the rear of the signal 28. The closing of back con: tact 12 shunts the line wires ILW and 2-LW to the reai' of signal 28 as an additional precaution that the line relays DHRl and DDR are 'deenergized. The closing of back content 11 completes a path by which current flows from line wire lLW through back contact 11*, resistor 47, back contact 48 of relay ZSDR, lamp Y of signal 28 and winding of relay ZSDR from right to left to the line wire ZLW. This current flows in the winding of relay ZSDR from right to left in the direction proper to pick up the relay as indicated by the arrow placed on the relay winding. In this second form of the invention the line relay ZSDR and each of the other line relays are provided with the well-known make-before-break contacts and hence when the relay ZSDR is energized over its back contact, it is picked up and retained energized over its front contact. With relay ZSDR picked up closing its front contact 48, the signal circuit is switched from the lamp Y to the lamp G of signal 28 with the result that the signal displays a green light as a clear signal indication while the train is moving through the section 1T, the signal indication being substantially continuously visible to the train operator. 7

Similarly when the train enters the section 2T and the track relay 2TR is shunted closing back contacts 24 and 25, the closing of back contact 24 completes a circuit path through which current flows first from the line wire lLW to the line wire ZLW through back contact 49 of the relay ESDR, lamp Y of signal 38 and winding of relay SSDR to the line Wire ZLW, and then flows through the front contact 49 and lamp G of the signal 3S when the relay 3SDR is picked up with the result that the signal 35 displays a green light as a clear signal indication to the train as it moves through the section 2T, the indication being substantially constantly visible to the train operator for the full length of the section. In a similar manner the line relays iSDR, ESDR, 6SDR, 7SDR and 8SDR are energized and picked up in response to the train entering the associated track circuit and the auxiliary signals 48, 58, 63, "7S and are illuminated one at a time to display agreen light as a clear signal indication, each signal indication being constantly visible to the train operator due to the relatively short length of the associated track section. When the train enters the last section 8T, it shunts the track relay STR. The closing of back contact 53 of relay 8TR prepares the circuit for the signal 98 and that signal displays a green lamp G or a yellow lamp Y according as the line relay EDR is released or picked up dueto polarity of the current supplied to the line circuit 3LW4LW.

It is apparent that when this train passes to the block next to the right and vacates the block D- E, current of negative polarity is supplied to the line circuit 1LW ZLW because at this time the line relay EHRl is released.

This line circuit current causes the line relay DHRI to be energized and picked up so that current of positive polarity is then supplied to the line circuit 5LW-6LW. Assuming that at this time a second and following eastbound train appraches the block D-E to shunt the relay ATR, the line relay DDR will not be picked up because the line circuit lLW-2LW is supplied with cur-rent of negative polarity and this current flows in the winding of relay DDR from right to left and in a direction which causes the relay to be held in its released position. Thus the circuit for the lamp Y of signal 18 is completed at this time and the signal 18 displays a yellow light as an approach signal indication to the following train. Further assuming that the first train remains in the block next in advance and the second train advances through the block D-E, the shunting of the track relay lTR completes a circuit through the winding of the relay ZSDR at signal 2S, but the relay ZSDR is not picked up because the line circuit current flows in the position due to its polar bias. Consequently, the signal Winding from left to right and in a direction to hold the relay in its released displays a yellow light as an approach sig-nal indication to the following train as it advances through the section 1T. Similarly, each of the line relays SSDR to SSDR is retained released when the following train enters the corresponding track section with the result that the circuit for the Y lamp of each of the signals to SS is closed and each signal discloses a yellow light as an approach signal indication.

It is also apparent that in the event the leading train moves east out of the block' next in advance so that the relay EHRI is picked up causing current of positive polarity to be supplied to the line circuit 1LW2LW, the line relay for the track section which the following train happens to be at the time occupying will be picked up causing the circuit for the associated auxiliary signal to be changed from displaying a yellow light to displaying a green light. Furthermore, on the assumption that no following train occupies the block D B when the first train moves out of the block next to the right and the current supplied to the line circuit 1LW-2LW is pole changed, the line relay DHRll is retained in its pickup circuit during the pole changing operation because of the characteristics of the relay and there is no so-called tumble down action of the line circuits to the rear of the block DE.

In this second form of the invention the block signals Is at location D and 98 at location E may be simplified and made two-position short range signals provided with a green lamp G and a yellow lamp Y powered from the line circuit the same as the other wayside signals. When thus simplified, each wayside signal of a block to the rear of a train occupying the block will be dark, a dark signal requiring a following train to move at low speed prepared to stop short of a train ahead.

Again, it is obvious that in Figs. 2a and 2b, the polar biased relays ZSDR to 3SDR may be equipped with contacts of the usual construction in place of the makebefore-break contacts disclosed, and the lamp circuits of the associated wayside signal energized from a local current source controlled over contacts of the relay. In this case, the winding of each polar biased relay would be connected across the line circuit over a back contact of the associated track relay.

Furthermore, it is obvious that each of the polar biased line relays ZSDR to 8SDR of Figs. 2a and 2b may be replaced with a three-position polar relay means and the wayside signals 28 to 8S made three-position signals having their lamp :circuits energized from a local source controlled by the three-position relay means.

. In the second form of the invention there is disclosed apparatus that may be provided for enforcing reduced speeds at curves and other permanent hazards. To this end the trackway apparatus includes inductors which have operative relation with train-carried equipment such as that disclosed in Fig. 3. Looking at Figs. 2a and 2b, trackway inductors are provided at spaced points and preferably the arrangement is such that the inductors are located one at the entrance end of each track section, but the invention is not limited to this arrangement and certain ones of the inductors at least may be located otherwise. These inductors are identified by the reference characters 1D to 90, inclusive, plus an additional induc tor AD in the rear of block DE. Each of these inductors would be preferably mounted on the ties just outside of one of the running rails where it is outside of the equipment clearance line of the railway. Ordinarily each trackway inductor comprises a winding mounted on a magnetic core having upstanding pole members. For example, the inductor 1D comprises a winding 55 mounted on a magnetic core 56 having upstanding pole members 57 and 58. The winding 55 is provided with a short circuiting path which includes front contact 59 of the line relay DDR. Thus when this relay DDR is picked up under clear traffic conditions, the winding 55 is short circuited and under approach trafiic conditions when the relay DDR is released, the winding 55 of the inductor is open circuited. As will appear shortly, when the inductor winding 55 is short circuited, it exerts a clear signal influence on the train-carried apparatus and when the winding is open circuited it exerts a restrictive signal influence on the train-carried apparatus. It is apparent that an inductor having no winding and comprising a magnetic core only exerts a restrictive influence on the train-carried equipment. inductors having no windings I shall call dummy inductors as an aid in describing the operation of the apparatus. Each of the inductors provided for the block D-E is provided with a winding similar to the inductor 1D except for the two inductors 4D and 8D which are dummy inductors located in a manner to appear hereinafter. In this form of the invention, a dummy inductor is provided at some distance to the rear of the entrance end of each block and the dummy inductor AD is located a specified distance to the rear of the location D. Furthermore, in the approach to a curve at which a maximum speed is prescribed, two dummy inductors are located and spaced apart a distance such that the time consumed by a train in traveling from one dummy inductor to the other must be an interval greater than a predetermined time interval and which interval is equal to that traveled by a train moving at the speed prescribed for the curve the train is approaching. That is, if the train consumes a time interval less than the predetermined time interval in traveling from the first to the second dummy inductors as it approaches the curve, it is traveling at a speed higher than the maximum speed prescribed for the curve.

I shall assume that a curve begins at the location E and extends eastwardly and a maximum speed less than the permissible maximum speed for the railway is prescribed for the curve. This curve territory is indicated in Fig. 2b by a dotted line 6 3C. To enforce this reduced speed at the curve 69C, the two dummy inductors 4D and 8D are located at selected points which in the drawing are the entrance ends of the sections 4T and ST, respectively, the location of the inductor 8D being some distance to the rear of the beginning of the curve so that there is sufficient distance to reduce the train speed by an automatic application of the brakes of the train if the train is traveling too fast. By way of illustration, it is assumed that the maximum permissible speed of the railway is 100 .iles per hour and that the prescribed maximum speed at the curve 60C is 60 miles per hour. Under this assumption the two inductors 4D and 8D may be spaced, say, 5280 feet apart and a preselected time interval for the train to consume in traveling from inductor 4D to 8D is set at 60 seconds. It is to be pointed out that the dummy inductor AD located to the rear of the entrance end D of the block DE is located a distance equal to the selected distance between the two dummy inductors 4D and 3D.

Referring to Fig. 3, which is a schematic view showing train-carried apparatus to cooperate with the trackway apparatus of Figs. 2a and 2b, the apparatus comprises as essential elements an inductor TD, a master relay PR, a brake controlling magnet valve MV, a time element relay TER, a slow release relay TEPR, another relay TSR which is also slightly slow releasing, and a power source, such as a battery, having positive and negative terminals B and N, respectively. The inductor TD comprises a winding 70 mounted on a magnetic core 62, having inverted pole members 63 and 64, it being pointed out that the inductor TD is mounted on the train so that its pole members pass over and mate with the upstanding pole members of the trackway inductors with some clearance, such trackway and train-carried inductors being widely used in intermittent train control systems.

The master relay PR is a two winding polar stick relay, such relay being characterized in that its contacts remain in the position to which they were last moved when the relay is deenergized. This relay is also characterized that once the relay is supplied with current it causes the 13 contacts to be operated and movement of the contacts oncefstarted, their movement is completed even though the current supplied to the relay to start the movement is interrupted.

.Normally the relay PR and the magnet valve MV are energized by a circuit extending from terminal B over wire 65, front contact 66 of relay TEPR, wire 67, lefthand normal contact 68 of relay PR, top Winding 69 of the relay, winding 70 of the inductor, winding of the magnet valve MV and to terminal N of the power source. The magnet valve MV is of the standard arrangement and is provided with means by which the valve when energized retains a port closed and the train brakes release, but once the magnet valve is deenergized and released the port is open to initiate a full service brake application of thetrain brakes. It is to be noted that the magnet valve MV is provided with a half wave rectifier element 84 connected across the winding of the magnet valve to provide the magnet valve with slow acting characteristics such that the magnet valve is not immediately moved to initiate a brake application when the magnet valve is deenergized, there being a predetermined delay in the initiating of the train brakes.

The time element relay TER is preferably of the type similar to the construction described in Letters Patent of the United States No. 1,966,965, granted to B. Lazich et ah, July 17, 1934, for Electn'cal Relays. It is sufficient for the present application to point out that when the relay TER is deenergized its armature immediately moves to a released or starting position where a check contact 71 and back contact 72 are closed, and that when the relay is energized for a predetermined time interval, it is operated to an extreme position where the back contact 72 is opened and front contact 73 is closed, the checking contact 71 being opened shortly after the initiation of the operation of the relay. It is here assumed for the purpose of illustration that the relay TER closes its front contact 73 and opens its back contact 72 after the relay has been operated for a time interval of 60 seconds. The relay TER is provided with a simple energizing circuit that includes normal contact 74 of the master relay PR and since the master relay PR is normally retained at its normal =or left-hand position, the timing relay TER is normally operated to its extreme position. With front. contact 73 of the relay TER closed the slow release repeater relay TEPR is energized by a simple circuit including the front contact 73. The apparatus may include a warning signal bell SB which is energized by an obvious circuit.

Assuming that the track apparatus of Figs. 2a and 2b is normal, that is, the block D-E and the block in advance are unoccupied, and an eastbound train provided with the apparatus of Fig. 3 enters the. block DE, the apparatus of the train being in its normal condition, the winding 55 of the inductor 1D is shortcircuited with the result, that the, influence transmitted from the trackway inductor 1D to the train inductor TD as the two inductors pass each other is of such a nature that the relay PR is retained energized in its normal position and there is no change in the condition of the train-carried apparatus. This same action will be repeated at the trackway inductors 2D, and 3D. However, when the train inductor TD passes: the dummy; inductor 4D, the influence created by the dummy inductor on the train-carried inductor causes the relay PR to be operated to its right-hand or reverse position. .The opening of the normal contact 68 of the relay PR causes the relay PR to remain deenergized as the train-carried, inductor TD moves beyond the trackway inductor 4D. The opening of the normal contact 74 of relay PR deenergizes the time element relay TER and it is immediately reset to its starting position where the check contact 71 and the back contact 72' are closed. The opening of front contact 73 of the time element relay TER deenergizes the repeater; relay TEPR but this relay remains picked, up for a time interval due to its slow release characteristic. Another energizing circuit for the 14 master relay PR is now completed from terminal B through wire 65, front contact 66 of relay TEPR, check contact 71 of relay TER, lower winding 75 of the master relay PR and reverse contact 76 of the relay to terminal N. This energizing of the lower winding 7 5 of the master relay causes the relay to be operated back to its normal position closing the previously traced circuit for energizing the relay through its upper Winding 6?. During the slow release period of the relay TEPR the stick relay TSR is energized by a pickup circuit including front contact 77 of the repeater relay TEPR and back contact 72 of the time element relay TER. Then when the relay TEPR is released at the end of its slow release period the stick relay TSR is energized and held picked up by a stick circuit including back contact 7 8 of the relay TEPR, normal contact 79 of the master relay and front contact 80 of the stick relay TSR. Hence when the repeater relay TEPR releases to open front contact 66, the master relay is retained energized by a circuit that includes terminal B,

wire 81, front contact 82 of the stick relay TSR, normal contacts 83 and 63 of the master relay, top winding of the relay 69, inductor winding 70, winding of magnet valve MV and negative terminal N. This circuit is effective to retain the relay PR in its normal position while the time element relay TER is operated from its starting to its extreme positions during the 60 second timing period. When the train passes the inductors 5D, 6D and 7D, the relay PR is retained at its normal position because the winding of each of these track inductors is short circuited under the traflic conditions.

I shall next assume that the train has reduced its speed by an application of the brakes by the train operator and is traveling at less than 60 miles per hour and consumes more than the 60 seconds in moving from the inductor 4D to inductor 81) so that the time element relay TER is operated to its extreme position and closes front contact 73 and opens back contact 72 before the train reaches the inductor 8D. This means that the repeater relay TEPR is energized and the stick relay T SR is deenergized and released and the master relay is retained energized in its normal position by the first traced circuit. Hence when the train passes the dummy inductor 8D, the traincarried apparatus is operated in the manner previously described in connection with the inductor 4D and a new operation of the time element relay TER is initiated but there is no brake application. Hence when the train passes the inductor 9D under the clear traflic condition, the relay PR is retained at its normal position and the train may proceed without further action on the part of the signal equipment because the train operator has already reduced the train speed to a speed less than the maximum permissible speed for the curve 60C.

Assuming that after the train passes the inductor 4D and the time element relay TER is reset and its operation started, the train continues at a high speed and reaches the inductor 8D in less than 60 seconds and before the time element relay TER has operated to open its back contact 72 and close front contact 73.

Under these circumstances the master relay PR is operated to its reverse or right-hand position at inductor 3D and remains in that position because the circuit including the front contact 66 of the repeater relay TEPR is open. With the master relay PR retained operated to its reverse position the magnet valve MV is shortly released and an autmoatic application of the train brakes effected to reduce the train speed before it enters the curve 60C. It is to be observed that the train operator can forestall the automatic application of the train brakes by making a full service application of the brakes in the usual manner and by which a contact 85 operated by the train operators brake valve is closed so that current flows from terminal B through wire 65, contact 85, check contact 71 of the time element relay, lower winding 75 and reverse contact 76 of the master relay to terminal N. This circuit causes the relay PR to be operated to its normal position so that the magnet valve MV is again energized and an automatic application of the train brakes avoided.

Assuming an eastbound train approaches the block DE under approach traific conditions and the winding of inductor 1D is open so that this inductor will transmit a restrictive influence to the train-carried apparatus, an automatic application of the train brakes will be eifected unless the train has already reduced its speed. This is so because as the train passes the dummy inductor AD in the rear of the entrance to the block DE the master relay PR is operated to its reverse position and an opera tion of the time element relay TER is initiated. If the train approaches the block DE at a high speed and has traveled the distance between the inductors AD and 1D in a time interval less than the operating time of the time element relay TER, then an automatic brake application will be effected at the inductor 1D, the operation being similar to that described in connection with a high speed train passing inductor 3D. However, if the train operator has taken action and so reduced the train speed as it approaches the approach signal 15 and the time element relay TER has completed its operation and closed front contact 73 so that the repeater relay TEPR is reenergized, then the train can pass the inductor 1D without an automatic application. However, at the inductor 1D, the time element relay TER will be reset and a new operation initiated to check that the train speed is low and the time consumed in reaching the inductor 2D is suflicient for the time element relay to complete its operation. It follows that the train speed is checked at each of the inductors in the block DE under approach traflic conditions.

Although I have herein shown and described certain forms of railway signal systems embodying my invention, it is to be understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In a railway signal system for a stretch of railway over which trafiic normally moves in a given direction, means to form therails of said stretch into consecutive insulated blocks, means to form the rails of each said block into several adjoining track sections, wayside signals one for each side section, each said signal adapted to display a clear or a restrictive indication and located adjacent the entrance end of the associated section, each eaid section having its length determined according to the curves of the track of the section to assure the signal next in advance is visible for substantially the full length of the section, a track circuit for each section including the scection rails and a track relay responsive to occupancy of the section; a single line circuit for each said block including a pair of line wires extending throughout the block, a front contact of each track relay of the block, a single power supply means connected to the line wires at the exit end of the block and a line relay means connected to the line wires at the entrance end of the block; each line relay means having contacts interposed in the connection of the power supply means for the line circuit next in the rear to control the polarity of the current supplied to that line circuit, a polar line relay for each said signal having connections to the line circuit for the same block, and operating circuit means for each said signal having connections to the signal and including contacts of the associated polar line relay to operate the signal to its clear or restrictive indication according to the polarity of the line circuit current.

2. In a railway signal system for a stretch of railway over which trafiic normally moves in a given direction, means to form the rails of said stretch into consecutive insulated blocks, means to form the rails of each said block into several adjoining track sections, wayside signals one for each section, each said signal adapted to display a' clear or a' restrictive indication and located adjacent the entrance end of the associated section, each said section relatively short'and of a length which enables the signal next in advance to be substantially constantly visible for the full length of the section irrespective of curves, a track circuit for each said section including a track relay and the section rails; a single line circuit for each said block including a pair of line wires extending only throughout that particular block, a source of current connected to the line Wires at the exit end of the block and a line relay means connected across the line wires at the entrance end of the block; each said line relay means having contacts interposed in the connection of the source of current for the line circuit next in the rear to control the polarity of the current supplied to that line circuit, a polar line relay for each said signal and having connections to the line circuit for the same block through contacts of the track relay for the same section, and operating circuit means for each said signal having connections to the signal and including contacts of the polar line relay for the same signal.

3. In a railway signal system for a stretch of railway over which traflic normally moves in a given direction, means to form the rails of the stretch into consecutive insulated blocks, means to form the rails of each block into a series of several adjoining insulated track sections, a track circuit for each said section including a power source and atrack relay connected across the section rails, the track relay being energized or deenergized according as the section is not or is occupied, a wayside signal for each said section adapted to display a clear or a restrictive indication, each said signal located adjacent the entrance end of the associated section, each said section relatively short and having a length determined according to the curves of the track to enable the signal next in advance to be visible for the full length of the section, a single line circuit for each said block including a pair of line wires extending the full length of the particular block only and having a front contact of each track relay in the block interposed in at least one of the line wires, supply means at the exit end of each block including a source of direct current and contacts of a relay responsive to traffic in the block next in advance, said supply means having connections to said line wires to supply current of positive or negative polarity 'to said line circuit, a polar line relay for each said track section, circuit means for each said section including a back contact of the track relay for the section next in the rear to connect the polar relay across said line wires extending in advance of the section to energize the polar relay according to the polarity of the line circuit current, and operating circuit means for each said signal including contacts of the polar relay for the same section to operate the signal to display its clear or restrictive indication according to the polarity at which the polar relay is energized.

4. In a railway signal system comprising, a stretch of railway track over which traflic normally moves in a given direction, the rails of said stretch formed into a series of several relatively short track sections, a track circuit for each of said sections including a track relay connected across the rails adjacent the exit end of the section and a current source connected across the rails adjacent the entrance end of the section, a wayside signal for each of said sections located adjacent the entrance end of the section, each signal being visible'substantially the entire length of the section to the rear, a single line circuit including a pair of line wires extending the length of said stretch, means including a single source of direct current [and a tratfic controlled relay having connections to said line Wires adjacent the exit end of the stretch to supply current of either positive or negative polarity to the line circuit, each of said track relays having a front contact interposed in at1easta selected one of said line wires, a polar relay for each of said sections, circuit means for each of said sections including a back contact of the track relay for the section next in the rear to connect the polar relay for the same section across said line wires extending in advance of the section, and other circuit means for each said section including contacts of the polar relay for the same section to connect the wayside signal for the same section across said line wires extending in advance of the section.

5. In a railway signal system for a stretch of railway track over which traflic moves in a given direction, means to form the rails of the stretch of track into a series of several consecutive track sections, a wayside signal for each of said sections, each said signal being located adjacent the entrance end of the section and operable to display either a first or a second indication to trafiic moving in said given direction, said sections being relatively short to assure constant visibility of the signal next in advance under general weather conditions and irrespective of track curves and wayside hazards, a track circuit for each said section including a normally energized track relay responsive to traffic in the section, a single line circuit including two line wires extending the full length of said stretch, means including a single current source and a tralfic controlled device connected across said line wires [adjacent the exit end of the stretch to supply current to said line circuit, said traffic controlled device operable to different positions to impress on the line circuit current of a first and a second characteristic according to a first and a second traflic condition in advance of the stretch, a line relay for each of said sections, circuit means for each of said sections including a back contact of the track relay for the section next in the rear to connect the line relay across said line wires to energize the relay by said line circuit current, each said line relay operable to a first or a second position according to the first and second characteristic of the line circuit current, and operating circuit means for each of said signals having connections to the signal and including first and second position contacts of the line relay for the same section.

6. In a railway signal system comprising a stretch of railway track over which traflic normally moves in a given direction, a series of several consecutive track sections formed in the rails of said stretch, wayside signals one located at the entrance end of each of said sections, said sections having lengths selected according to the alignment of said track to provide substantially constant visibility of said signals one at a time to a train when traversing said stretch; a track circuit for each of said sections including the rails of the section, a track relay connected across the section rails adjacent the exit end of the section, and a current source connected across the section rails adjacent the entrance end of the stretch; a single line circuit including a pair of line wires eX tending along said stretch and having a front contact of each of said track relays interposed in at least one of said line wires, means including a direct current source and a trafiic controlled contact having connection to said line wires adjacent the exit end of said stretch to supply current of positive or negative polarity to said line circuit, polar line relays one for each of said sections, circuit means for each of said sections including a back contact of the track relay for the section next in the rear to connect the line relay for the same section across said line wires to energize the line relay at positive or negative polarity according to the polarity of the line circuit current, and operating circuits for each of said signals including contacts of the line relay for the same section.

7. In combination, a first and a second adjoining railway track section over which trafiic normally moves in a given direction, a wayside signal adapted to display a clear and a restrictive indication located at the exit end of each of said sections; a track circuit for each said section including the section rails, a current source connected across the rails adjacent the entrance end of the section and a track relay connected across the rails adjacent the exit end of the section; a single line circuit including a pair of line wires extending along the sections, a current source and tralfic controlled pole-changing contacts connected across the line Wires in. advance of the sections for supplying current of positive or negative polarity to the line circuit; each said track relay having two front contacts one interposed in each of said line wires, asymmetric units one interposed in series in a selected one of the line wires immediately in advance of the front contact of each track relay interposed in said selected line wire, each said asymmetric unit poled to pass in the forward direction line circuit current of negative polarity, a polar biased line relay connected in multiple with each said asymmetric unit and poled to be effectively energized by line circuit current of positive polarity, circuit means for each said polar relay including a back contact of the track relay for the section next in the rear connecting the polar relay across the line wires for efiective energization of the relay by line circuit current of positive polarity, and a clear and a restrictive operating circuit for each of said signals including a front and a back contact respectively of the polar relay at the same location and a back contact of the track relay for the section next in the rear connecting the operating circuits across the line wires.

8. In combination, a first and a second adjoining railway track section over which traflic normally moves in a given direction, a wayside signal adapted to display a clear and a restrictive indication located at the exit end of each of said sections; a track circuit for each said section including the section rails, a current source connected across the rails adjacent the entrance end of the section and a track relay connected across the rails adjacent the exit end of the section; a single line circuit including a pair of line wires extending along the sections, a single current source and traflic controlled pole-changing contacts connected across the line wires in advance of the sections for supplying current of positive or negative polarity to the line circuit; each said track relay having two front contacts one interposed in each of said line wires, a polar biased line relay for each of said signals; circuit means for efiectively energizing each of said polar relays by line circuit current of positive polarity and including a back contact of the track relay next in the rear, a make-before-break contact of that polar relay, the clear position of the associated signal and the winding of the polar relay in its effective direction; and other circuit means for connecting the restrictive position of each said signal across the line wires and including a back contact of the track relay next in the rear, a back contact of the associated polar relay, the restrictive position of the signal and the winding of the associated polar relay in its non-effective direction.

Lay Ian. 26, 1932 Bushnell July 28, 1942 

